Due to competition in freight carrier services by rail, sea and air, the trucking industry has been strongly concerned about the efficiencies of their own system. In recent years, the cost of truckage has increased as a result of increased fuel cost and mandated lower speed limits eventuating from fuel shortages. One approach to offsetting such increased costs is to decrease vehicle fuel consumption.
Fuel consumption of the freight-hauling truck tractor and trailer combinations is a function of weight, engine efficiency and air drag. Since the freight capacity must be maintained at a high level in order to satisfy the economics of trucking, the size and, thus, the weight of the truck combinations cannot be decreased enough to result in substantial fuel savings. Of course, improvements in engine efficiency will always be made but they are not sufficient by themselves to eliminate the burden caused by weight and air drag. Air drag at the rear end of the vehicle is a very important cause of poor fuel consumption. A truck tractor and trailer combination which gets about four miles to the gallon loaded, for example, may only get four and one-half miles per gallon unloaded when operated at the same high speed. It is known that this mileage can be increased by placing an air deflector above the cab of the truck trailer and by placing a drag reduction device at the rear end of the truck trailer, as illustrated in my U.S. Pat. No. 4,142,755. It is also known in the field that drag reduction devices designed for the rear end of vehicles must be removed and stored when not used. Further redesigning and modifications to the present designs for the drag reduction devices on long distance hauling vehicles will greatly reduce the air drag and thus, reduce fuel consumption and increase the ease of use of these devices.